1. Field of the Invention
The present invention generally relates to graphics processing and more specifically to computing plane equations for primitive shading after non-visible pixels are removed by z culling operations.
2. Description of the Related Art
In conventional graphics processing systems, plane equations for primitives are computed after primitives that are outside of the viewport frustum are culled. The plane equations are computed before z culling operations that determine visibility of primitives based on z-buffering. Consequently, plane equations may be computed for primitives that are culled during z culling operations and do not contribute to the final image. However, delaying computation of the plane equations until the z culling operations are complete delays primitive shading that relies on the plane equations and necessitates buffering of the vertex data that is used to compute the plane equations.
Accordingly, what is needed in the art is a technique for computing plane equations for primitive shading after non-visible pixels are removed by z culling operations.